Rare earth-doped glass microbarcodes

Abstract

The development of ultraminiaturized identification tags has applications in fields ranging from advanced biotechnology to security. This paper describes micrometer-sized glass barcodes containing a pattern of different fluorescent materials that are easily identified by using a UV lamp and an optical microscope. A model DNA hybridization assay using these ''microbarcodes'' is described. Rare earth-doped glasses were chosen because of their narrow emission bands, high quantum efficiencies, noninterference with common fluorescent labels, and inertness to most organic and aqueous solvents. These properties and the large number (>1 million) of possible combinations of these microbarcodes make them attractive for use in multiplexed bioassays and general encoding. Encoded bead bioassays are emerging as an attractive alternative to traditional slide-based microarrays because beadbased bioassays offer multiplexing of both probes and samples (the ''analyte''), and they have significantly fewer drawbacks related to mass transport-limited binding of analytes to the immobilized probes. Several approaches have been described for the fabrication of encoded beads: those in which the coding material is randomly distributed in the bead (1, 2) and those in which the coding material is present in a defined pattern on the bead (3). Because different patterns of the same coding materials (e.g., position and thickness of metal stripes on cylindrical particles) result in distinguishable beads (3), a larger number of uniquely encoded beads can be obtained relative to beads with randomly distributed coding materials (e.g., polymer beads infused with mixtures of quantum dots) (2).Current methods for fabricating encoded beads are limited in terms of either the number of possible codes or the compatibility of the beads with bioassays and fluorescence detection. The most widely used method for making encoded beads, infusing polymer microspheres with mixtures of fluorescent dyes in predefined ratios, is not well suited for the fabrication of large (Ͼ10 5 ) numbers of uniquely distinguishable beads. Trau and coworkers have used silica microspheres containing fluorescent dyes for encoding polymer beads by using split-pool methods, and have also described the formation of dye-doped concentric silica layers around core silica particles (4). There are only a limited number of spectrally well-resolved dyes that do not also interfere with commonly used biological labels. Moreover, measurements of intensities and their ratios are inherently difficult, which limits the number of levels at which a dye can be incorporated to give distinguishable beads. Mixtures of quantum dots embedded in polymer microspheres offer significant advantages over conventional fluorescent dyes because they are relatively more photostable and have narrow emission linewidths (2). However, quantum dots are made of toxic materials (e.g., CdS, CdSe, CdTe) (5), and difficulties distinguishing between codes based on different amounts of the same quantum dots are similar to those ...

High capacity tagging using nanostructured diffraction barcodes

“…Methods using magnetic tagging are also being investigated [6]. In particular, multicolor optical coding has been achieved by embedding quantum dots of zinc sulfide-capped cadmium selenide nanocrystals into beads [7][8][9][10] while patterns can also be written in fluorescently dyed beads by spatially selective photo-bleaching to create spatially selective fluorescent tags [11]. Here we describe a new method for encoding small beads which allows for non-contact reading.…”

Multiplexed Immunoassays

“…An ideal microparticle encoding technique must satisfy a number of requirements, it must be: 1) machine-readable (decoding); 2) unaffected by the biochemical reactions; 3) robust, with low error rate; 4) able to encode large numbers of particles, each with a unique code; 5) are compatible with biomolecule attachment; and 6) able to mass production with low-cost. To this end, since the 1990s, different technologies for multiplexing have emerged (optical [19][20][21][22][23][24][25][26][27][28] , graphical [29][30][31][32][33] , electronic 34,35 , or physical 36, 37 encoding) for different platforms (flow cytometry or fluorescence microscopy). The features of each encoding strategy are listed in Table 1.…”

Development of Micromarkers with Various Photoluminescence Colors as Tracers for Shadowing Pursuits

“…Although the photoluminescence intensities of NdBFA3 and YbBFA3 were much weaker (approximately 1/500 -1/1200) than those of EuBFA3 and TbSE3, their photoluminescence peaks were detected at approximately 875 (the 4 F3/2 → 4 I9/2 transition of Nd 3+ ) and 975 nm (the 2 F5/2 → 2 F7/2 transition of Yb 3+ ), respectively. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] The photoluminescence intensities of NdBFA3 and YbBFA3 were especially weak, because the UV light at 365 nm was not the optimum excitation light for the near-IR photoluminescence. However, the wavelength of the UV light lamp was used most popularly as an excitation light is 365 nm.…”

“…Eu 3+ and Tb 3+ complexes have been prepared by many researchers in various fields, and characteristically emit red and green luminescence under UV light at approximately 365 nm, respectively. [3][4][5][6][7][8][9][10][11][12][13][14][15] The retina of the human eye has three types of receptors: one for red, one for green, and one for blue light, and receives a mixture of two colors to form another color of light. For example, it forms yellow from red and green, magenta from red and blue, and cyan from green and blue.…”